A parallel plate capacitor with air between the plates has a . . .

Question : A parallel plate capacitor with air between the plates has a capacitance of 8µF. What will be the capacitance if the distance between the plates is doubled and the space between them is filled with a substance of dielectric constant K=2?


Doubt by Ananya

Solution : 

Case I
Area of each plate = A
Separation between the two plates = d
Permittivity of free space = ε
Capacitance = C₀=ε₀A/d=8µF

Case II
A'=A
d=2d
Permittivity of the medium = ε=Kε₀=2ε
New Capacitance 
C=
εA'/d'
C=Kε₀A/(2d)
C=2ε₀A/(2d)
C=
ε₀A/d
C=
C₀
C= 
8µF.

Hence, the new capacitance will remains equal to the initial capacitance of 8µF.



Similar Question : 

A parallel plate capacitor with air between the plates has a capacitance of 8 µF. What will be the capacitance if the distance between the plates is reduced by half, and the space between them is filled with a substance of dielectric constant 6?

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96µF